Low‐lying excited states of 7‐aminocoumarin derivatives: A theoretical study

Abstract

Excited states of three 7-aminocoumarin derivatives, coumarin 120 (7-amino-4-methylcoumarin), pyrrolyl coumarin 7-(1H-pyrrol-1-yl)-4-methyl-2H-1-benzopyran-2-one, and carbazole-coumarin hybrid 10H-4-methyl-2H-2-oxopyrano [5,6-b]carbazole, have been studied using B3LYP time-dependent density functional theory (TDDFT). The solvent effect has been taken into account using the polarizable continuum model. The spectra calculated using TDDFT agree well with the experimental absorption spectra. The electronic structures and the solvent effect for the low-lying singlet excited states have been investigated. The HOMO of the pyrrolyl coumarin is localized on the pyrrolyl ring, while the HOMO in the other 7-aminocoumarins is delocalized over the entire molecule. This leads to the weak fluorescence of the pyrrolyl coumarins found in experiments. The HOMO and next HOMO in carbazole-coumarin hybrids have similar orbital energy values, which is not the case in the other 7-aminocoumarin derivatives. This leads to the additional peaks found in the 30,000 -40,000 cm Ϫ1 region of the observed absorption spectra, which are specific for carbazole-coumarin hybrids.

Theoretical studies on absorption, emission, and resonance Raman spectra of Coumarin 343 isomers

“…In the past decades, in fact, stable ground states and pure electronic absorption spectra of coumarin derivatives in gas phase and in solution have been studied by using quantum chemical methods. [32][33][34][35][36][37][38][39][40][41][42][43] For instance, in the framework of density functional theory (DFT), Preat et al 33 investigated the UV electronic absorption spectra of substituted coumarins with various basis sets and functionals. It turns out that the Becke-Lee-Yang-Parr functional (B3LYP) together with the polarized continuum model (PCM) provides valid ground-state geometries and the consistent UV spectra with experimental measurements.…”

Development of a Novel Fluorophore for Real-Time Biomonitoring System

“…Coumarins are an important group of organic compounds that are used as additives to food and cosmetics, optical brightening agents, and dispersed fluorescent and laser dyes [47], [48]. A number of 7-aminocoumarin derivatives bearing an aromatic or heteroaromatic radical in the 3-position serve as valuable fluorescent dyes [49].…”

Synthesis of Chromeno[4,3‐b]pyrrol‐4(1H)‐ones, from β‐Nitroalkenes and 4‐Phenylaminocoumarins, under Solvent–free Conditions

“…In agreement with this report, we observed that the emission spectra of 1 a and 7 were of rather low intensity, in the blue region, and exhibited essentially the same shape and position of their maxima (467/468 nm, with half band widths of 74 and 84 nm, respectively), suggesting that the different organic moieties in the coumarins did not play a fundamental role in the excited state of these compounds . The low emission intensities are not fully unexpected; it has been recently noticed that pyrrole‐fused coumarins show little fluorescence …”